U.S. Pat. No. 2,303,968, issued to E. L. C. White on Dec. 1, 1942, discloses a method and apparatus for the removal of pulses which were added tea video signal for the purpose of controlling an automatic gain control. These automatic gain control (AGC) pulses were removed "[i]n order to eliminate at the receiver undesirable effects due to the pulses . . . " (page 1, left column, line 41).
In general, White removed these AGC pulses ". . . by mixing them with the line synchronizing signals which are separated, delayed and/or broadened for this purpose" (Ibid. line 45). He used a delay line to delay the synchronizing pulses and, optionally, a multi-input diode OR gate connected to taps on the delay line to broaden the pulses. An inverting stage and a mixing stage, which mixed the locally generated pulses "in the negative sense" with the input video, completed his circuit.
While White's original arrangement can be implemented with modern semiconductors, certain deficiencies are present. First, use of a mixing circuit requires that the locally generated pulse amplitude precisely matches the pulse amplitude on the incoming video. If resistive mixing is used, then exact matching of pulse duration and location is also critical. Any mismatch will result in some residual pulse or part thereof at the output. Second, the delay line provides only discrete steps in pulse delay and/or pulse broadening. Third, should a pulse be absent from the input video, his circuit will add a large negative going pulse in its place which would interfere with the synchronization signals.